The Microsoft Windows Installer is an installation and configuration service that ships as part of the Microsoft Windows 2000 operating system, and is provided as a redistributable product for Microsoft Windows 95, 98, ME, and NT version 4.0.

Windows Installer enables software users to efficiently install and configure products and applications. The installer can also provide software products with new capabilities to advertise features without installing them, to install products on demand, and to add user customizations. The Windows Installer supports advertisement of applications and features according to the operating system.